Method of attaching parts



R. POLIVKA METHOD 0F ATTACHING PARTS Filed May 5, 1937 /A/ VIA/70A H. Pom/KA Hf?. WM

Oct. 24, 1939.

' Patented Oct. 24, 1939 liIETHOD F lA'ITAC'HING PARTS Rudolph Polivka, Berwyn, Ill., assigner to Western Electric Company, Incorporated, New York, N. Y.; a corporation of New York i Application May 5, 1937, serial ivo/140,905

aclaims. (o1. zii-155.55)

'This invention relates to methods of attaching parts, and more particularly t0 a method of securing actuating and separating studs to electrical contact springs.

An object of this invention is to provide an ex` peditious, eflicient, and economical method of firmly attaching parts, particularly actuating and separating studs to electrical contact springs.

In accordance with the above object, the invenlO tion in one embodiment thereof as appliedto the attaching of cylindrical hard rubber actuating and separator studs having a uniform diameter throughout their length to iiat resilient metallic Contact springs of electromagnetic switching devices, contemplates a method wherein the contact spring is provided with an aperture which is slightly larger in diameter than that of the stud. The stud is inserted in the contact spring aperture with its ends extending from opposite sides of the spring and while the parts are predeterminedly positioned relative to each other and maintained the metal of the spring at each side thereof surrounding the stud is contemporaneously pressed annularly and caused to flow in` wardly toward the center of and become slightly embedded in the stud by cold pressing the metal by means of a movable hollow annular staking punch and cooperating stationary die upon which the spring is mounted, thus firmly attaching the parts together.

Other objects and advantages of this invention will more clearly appear from the following detailed description, taken in connection with the accompanying drawing, wherein Fig. l is a fragmentary vertical sectional View through one type of an electromagnetic switching device having contact springs with actuating and separating studs attached thereto in accordance with the method of this invention;

40 Fig. 2 is a fragmentary side View of an enlarged scale of one of the contact springs with its attached stud;

Fig. 3 is a fragmentary diagrammatic view on an enlarged scale, partially in section, of the contact spring and stud shown supported on the stationary lower die ready to be attached together, the movable upper punch being shown approaching the spring to stake the spring and the stud together, and

Fig. 4 is a view similar to Fig. 3 after the staking operation has been performed.

Referring now to the drawing, and particularly to Fig. 1, there isfragmentarily shown one type of electromagnetic switching device, comprising an assembly or pile-up of flat resilient metallic contact springs I0,"each having secured at its upper free end a. contact II, the springs at their opposite lower ends having terminal portions I2. 'I'he springs I0 are suitably predeterminedly spaced and insulated from leach other as well as 5' from a metallic supporting member I3, shown fragmentarily, and secured in parallel positions by means of a screw I4. Associated with the contact ends of the springs III is a row of fixed metallic plates I5 having extensions I6 carrying a contact I1, each contact arranged to be engaged by the opposite contact II on the spring I0 upon actuation of the springs to close circuits through the contacts II and I'L The plates I5 are suitably predeterminedly spaced and insulated from each other as well as from a metallic supporting member I8 and maintained in parallel positions by a screw I9.

The springs III near their upper contact ends are maintained in predetermined spaced relation 20 with the contacts I I carried thereby spaced from the fixed contacts I1 by a plurality of cylindrical hard rubber studs 25 having a uniform diameter throughout their length. In the particular arrangement of contact springs shown one stud 25 25 is secured to the spring I0 at the extreme leftside of the device, and another stud is secured to the third spring from the let side, each stud extending from opposite' sides of its spring support. In use all of the springs I0 are simulta- 30 neously flexed towards the left upon actuation of means (not shown) engaging and pressing against the short portion of the stud 25 which extends from the spring I0 at the left side of the device. The movement imparted to the springs is suiil- 35 cient to close each pair of contacts II and I'I, the studs 25 serving as actuators as well as sepa.- rators, as above described.

The present invention` is directed to a method of securing the cylindrical hard rubber stud 25 40 to the spring I0. In practicing the method of attaching the parts the spring I0 is provided with an aperture 26 (Fig. 3), the diameter of which is the same, or preferably slightly larger, than the diameter of the stud 25 which has a uniform 45 diameter throughout its length. With the parts ready to be attached they are properly positioned. as shown in Fig. 3, on a stationary lower die 21 formed with a cylindrical depression 28 of such diameter that it freely receives the stud 25, a bot- 50 tom fiat face 29 of the. depression serves as a support for the stud 25 while the spring with the stud extending through the aperture 26 thereof rests upon an annular raised wedge-shaped formation 30 formed on the die. A hollow movable 65 punch ll into which the stud 2l may freely enter is arranged above and in axial alignment with the die 21 for movement toward and from the die, the movement of the punch being effected by a suitable source of power (not shown). 'I'he lower annular surface of the punch Il is formed with an annular depending wedge-shaped formation 32 which is similar tn the formation Il on the die Il, only reversed, and is accurately aligned therewith. It is to be understood that the distance or depth of the outer surfaces of the ringshaped or annular formations l0 and l2 from -the faces of the punch and die Il and 21, respectively, which distances determine the degree of their penetration into the opposite sides of the spring Il, are such that the spring is not deleteriously l weakened, and further that the depths of the formations as well as the crosssectional shape thereof will vary with the thickness of the spring and other characteristics of the metal from which they are produced.

Opposite annular side portions of the spring IU surrounding the stud 25 are now contemporaneously subjected to pressure by the downward movement of the punch 3|, the ring and wedge-shaped formation 3l on the punch moving into engagement with the upper surface of the spring, the lower surface of which rests on the ring and wedge-shaped formation I2 on the die 21. In the continued downward movement of the punch 3l the opposite ring lformations 3Q and l2 are pressed into the opposite surfaces of the spring Il and the metal of the spring is caused to cold flow toward the center of and compietely around the stud 2i, filling the slight annular space between the inner and outer peripheries of the spring aperture 26 and the stud 25, respectively, and become slightly embedded throughout the thickness of the spring in the relatively softer material of the hard rubber stud, the points of greatest embedment being at the continuous peripheral edges of the aperture at each side of the spring, as clearly shown in Fig. 4, with the peripheral wall of the aperture being slightly concave between these points. Upon removal of the spring with the attached stud each side of the spring immediately surrounding the stud will have formed therein an -annular channel, I3 (Figs. 2 and 4) formed during the extruding of the metal inwardly into the stud.

it will be obvious in the particular application of the invention that the extruding of the metal of the spring i0 completely surrounding the aperture 26 inwardly and into the stud 25 at all points therearound in the manner described will result in a very ilrm attachment of the parts, thus eliminating loose assemblies while the electromagnetic switching device is in use with consequent interruption to service, and thereby reducing maintenance cost. Furthermore, by practicing the described method an expeditious, efllcient and economical assembly ,and attachmen of the parts are effected.

Although the invention herein described and illustrated is particularly well adapted for use in attaching contact springs and hard rubber actuating and separator studs, it will beunderstood that the invention is capable of many other modications and applications and is to be limited only by the scope of the appended claims.

What is claimed is: 4

1. A method of attaching a hard rubber stud to a flat electrical contact spring which comprises forming an aperture of predetermined size `in the spring, positioning the stud which is predeterminedly smaller in cross-sectional area than that of the aperture in the aperture with its ends extending frorn opposite sides of the spring, and then staking the metal of the spring upon a i'iat side thereof to cause the metal of the contact spring to flow inwardly simultaneously in ring formation around the stud and thereinto and thereby firmly attaching the stud to the spring.

2. A method of attaching a cylindrical hard rubber stud to an electrical contact spring which comprises forming an aperture of predetermined diameterin the spring, inserting the stud which is predeterminedly smaller in diameter than the aperture in the aperture with its ends extending from opposite sides of the spring, and then staking the metal of the spring upon a fiat side thereof toward the center of and into the stud simultaneously completely therearound and thereby firmly attaching the stud to the spring.

3. A method of attaching a cylindrical hard rubber stud to an electrical contact spring which comprises forming an aperture of predetermined diameter in the spring, inserting the stud which is predeterminedly smaller in diameter than the aperture in the aperture with its ends extending from opposite sides of the spring, and then coldpressing the metal of the spring upon opposite f lat sides and in opposite directions parallel to the longitudinal axis of the stud to cause the metal to flow inwardly simultaneously at each side ol the spring toward the center of and become embedded in the stud completely therearound and thereby firmly attaching the stud to the spring.

RUDOLPH POLIVKA.' 55 

